Mobile information terminal having operation keys and a display on opposite sides

ABSTRACT

A mobile information terminal has a front surface on which a display surface of a display device is arranged and a rear surface on which a plurality of operation keys are arranged. The mobile information terminal further has a half-depressing sensor for detecting that each of the operation keys is half-depressed and/or a touch sensor for detecting that each of the operation keys is touched. A control section executes a processing operation to cause the display device to display an image showing the arrangement of said operation keys and to change an icon which corresponds to a key of operation keys when a control section determines, according to an input signal from the half-depressing sensor or the touch sensor, that the finger of the operator is placed on this key of operation keys.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is continuation of U.S. application Ser. No.10/566,961 filed Jan. 27, 2006, which application is a 35 U.S.C. §§371national phase conversion of PCT/JP2004/010609 filed 26 Jul. 2004 whichclaims priority to Japanese Patent Application No: 2003-280996 filed 28Jul. 2003, all of which are incorporated herein by reference. The PCTInternational Application was published in the Japanese language.

TECHNICAL FIELD

The present invention relates to a mobile information terminal which isprovided with a built-in computer for executing various types ofinformation processing, an input device through which an operator inputsinformation, and a display device for presenting information to theoperator.

BACKGROUND ART

Recently, mobile information terminals represented by portabletelephones have come into widespread use. As shown in FIGS. 1A, 1B, suchportable telephones are provided with display devices 11, 21 fordisplaying information and an input device composed of operation keys12, 22, a pointing device (not shown) and the like. Portable telephone10, which is entirely encased in a single housing as shown in FIG. 1A,is known as one of portable telephones. Folding portable telephone 20,which has two casings that are jointed by a hinge as shown in FIG. 1Band which can be changed between an open state in which both casings areside by side, and a folded state in which both casings are foldedtogether for convenience of portability, is also known. In either case,display devices 11, 21 and the input device are usually disposed on thesame side as each other so that a user can operate the input devicewhile viewing display devices 11, 21. Further, keys and a pointingdevice may be arranged on a side surface facing a direction that isperpendicular to the surface on which display device 11, 21 aredisposed.

In contrast, a mobile information terminal, in which some operation keysare arranged on the rear surface (a surface placed back to back with thedisplay surface of a display device) of a surface on which a displaysurface of a display device is disposed, is disclosed in Japanese PatentApplication Laid-Open No. 2000-236376. Further, a mobile informationterminal, in which a touch panel is arranged on a rear surface, isdisclosed in Japanese Patent Application Laid-Open No. 2002-77357.

However, configurations, in which an input device is arranged either onthe same surface as the display surface of a display device of a mobileinformation terminal or on a side surface, as in the general prior art,have the following drawbacks:

(1) When a user holds a mobile information terminal in his/her hand,fingers of the hand holding the mobile information terminal extendaround the rear side of the mobile information terminal. Therefore,superior ease of operation cannot be achieved when the user wants tooperate an input device disposed on the side of a display surface of adisplay device with one hand holding the mobile information terminal.

(2) In a case where an input device is disposed on the side surface of amobile information terminal, because the side surface is narrow andprovides a restricted area for disposing the device, when an inputdevice for performing a complicated input operation, for example, apointing device to input values of two-dimensional coordinates isdisposed on the side surface, an operation to input information into thedevice by hand is apt to be difficult. In particular, an operation thatuses the finger(s) of one hand holding the mobile information terminalis apt to be difficult.

(3) In a case in which the user operates a mobile information terminalwith the fingers of one hand holding the mobile information terminal ina condition in which the user holds a mobile information terminal inhis/her hand, the user is only able to operate the terminal with some ofhis/her fingers, for example, an index finger, the thumb or the like,because the fingers of the hand are used to hold the mobile informationterminal. Therefore, operation efficiency is apt to be reduced.

(4) In a case in which a user performs an input operation while holdinga mobile information terminal in his/her hand, when the user performs aninput operation with a hand that is different from the hand holding themobile information terminal in order to avoid the problems (1) to (3),the user has both hands fully occupied. Therefore, the user cannot usethe hand(s) for other tasks. Further, there are cases where a user maywish to operate a mobile information terminal in a condition in whichonly one hand can be used, for example, a case where the user operates amobile information terminal while holding a bag. In this case, the useris forced to perform an input operation with one hand that holds amobile information terminal.

(5) In cases where a display device and an input device are disposed onthe same surface as each other, there is mutual competition forinstallation of each device on the area of the terminal whose size islimited so that the mobile information terminal can be manufactured in acompact configuration as a portable device. Under these circumstances,when the display device is made large to improve visibility, theinstallation space for the input device is narrowed, thus sacrificingease of operation. On the other hand, when the input device is madelarge to improve operability, visibility is sacrificed.

(6) In a case where a display device and an input device are disposed onthe same surface as each other, when both are made large to improve bothoperability and visibility, the mobile information terminal itself isrequired to be made large. Therefore, portability is reduced.

In contrast, in the prior art disclosed in above-mentioned JapanesePatent Application Laid-Open No. 2000-236376 and Japanese PatentApplication Laid-Open No. 2002-77357, the installation area for inputdevices disposed on a front side can have a margin to some degree byarranging a part of the input devices on a rear side, and thusoperability can be improved to some extent.

However, in Japanese Patent Application Laid-Open No. 2000-236376, onlylimited kinds of input devices are arranged on a rear side such as ascroll key, a determination key, a clear key and the like, and most ofthe keys are still arranged on the front side. On the other hand, whenoperating keys arranged on the rear side, since an operator views thedisplay device that is arranged on the front side, the operator cannotview his/her finger as it operates keys arranged on the rear side.Therefore, in cases where an increased numbers of keys are arranged onthe rear side, the input operation becomes difficult.

Further, in Japanese Patent Application Laid-Open No. 2002-77357, asshown in FIGS. 2A and 2B, in mobile information terminal 30, touch panel32 is disposed on surface 30 b opposite to surface 30 a on which displaydevice 31 is disposed. This touch panel 32 is used to select one itemamong selection items that are displayed on display device 31 bytouching the location on the rear side that is reverse to the locationwhere the item to be selected is displayed. In this configuration,various input operations can be performed by using touch panel 32disposed on the rear side. However, because the operator cannot view thefinger with which he/she is performing the operation, the operatorcannot determine precisely where the finger has been placed until theoperation to select one item has been completed. Therefore, particularlyin cases where there are many items to be selected and which are locatedin a narrow area, a mistake may be made in touching the location of theitem to be selected, and as a result, an item different from the oneintended is selected. Therefore, there is a problem in operability.

Further, there are cases where an operator can perform an inputoperation without viewing a display device during the input operation ofa mobile information terminal, for example, in cases where the operatorinputs a specific keyword. In this case, when the input device isdisposed on the rear side, it may be more convenient for the operator toperform an input operation while viewing the rear side. However, mobileinformation terminal 30 disclosed in Japanese Patent ApplicationLaid-Open No. 2002-77357 is not suitable for operating touch panel 32disposed on surface 30 b of the rear side while viewing mobileinformation terminal 30 from surface 30 b of the rear side. That is, inmobile information terminal 30 disclosed in Japanese Patent ApplicationLaid-Open No. 2002-77357, for example, when an input operation that usesalphabet is performed by using touch panel 32 of the rear side, as shownin FIG. 2A, the layout of areas that are used to input each letter,while mobile information terminal 30 is viewed from surface 30 b of therear side, is a mirror image of the layout of areas that are displayedon display device 30 while viewed from surface 30 a of the front side.Therefore, a problem arises in that the input operation confuses theoperator.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a mobile informationterminal wherein even if a large number of operation keys are disposedon a surface opposite to the display surface of the display device, anoperator can smoothly perform an input operation by using the operationkeys while viewing the display device. Further, another object of thepresent invention is to provide a mobile information terminal wherein,even when an operator performs an input operation by using operationkeys disposed on a surface opposite to the display surface of thedisplay device while viewing the surface opposite to the displaysurface, the operator can smoothly perform an input operation withoutbeing confused.

To achieve this object, a mobile information terminal according to thepresent invention comprises a display device and a plurality ofoperation keys. The display device and the operation keys are disposedon surfaces opposite to each other. The mobile information terminalfurther comprises finger position detecting mechanisms for detectingthat a finger of an operator is placed on each of the operation keys.Signals from these operation keys and the finger position detectingmechanisms are entered into the control section of the mobileinformation terminal. This control section is at least able to controloperation of the display device. The control section executes aprocessing operation that causes the display device to display an imageof the arranged operation keys and, when the control section sodetermines, based on an input signal from the finger position detectingmechanism, that the finger of the operator has been placed on any of theoperation keys, to change an icon which is included in the image of thearranged operation keys, that icon corresponding to the operation key onwhich the finger of the operator has been placed.

In this configuration, an operator, who intends to perform an inputoperation by using operation keys arranged on a rear side opposite tothe side of the display surface while viewing the display device, canrecognize one key of the operation keys on which the finger of theoperator performing the operation is placed before fully depressing theoperation key to confirm the input, by moving his/her finger on that keyof operation keys and by ascertaining that an icon of that key ofoperation keys displayed on the display device is changed due tomovement of the finger on that key of operation keys. Therefore, even ifa large number of operation keys are arranged on the rear side oppositeto the side of the display surface, the operator can smoothly perform adesired input operation without making any errors.

More specifically, a half-depressing sensor for detecting that each ofthe operation keys is half-depressed and/or a touch sensor for detectingthat the finger of the operator touches each of the operation keys canbe used as the finger position detecting mechanism. That is, before anoperator confirms that an input has been entered by fully depressing anoperation key, when the operator depresses an operation key to somedegree, that is, when the operator half-depresses the operation key, thehalf-depressing sensor can detect this action and thus can detect thatthe finger of the operator is placed on the operation key. On the otherhand, when the operator touches an operation key, the touch sensor candetect that the finger of the operator is placed on the operation key.

Specifically, executing a processing operation to change the icon thatcorresponds to the operation key, which is half-depressed or touchedwhen the finger of the operator is placed on, can be performed bychanging at least one of the following: the display color, the displayfigure, the display brightness, and the flickering pattern in thedisplay of the icon.

Further, the control section may execute a processing operation to startor stop a predetermined program stored in advance when determining thatthe finger of the operator is placed on a predetermined operation key,or when determining, according to a signal from the finger positiondetecting mechanism, that the finger of the operator is sequentiallyplaced on positions of a plurality of operation keys in a predeterminedorder, based on a signal from the finger position detecting mechanism,that is, when the operator performs a half-depressing operation or atouch operation for a predetermined operation key, or when the operatorsequentially performs half-depressing operations or touch operations fora plurality of operation keys in a predetermined order. Thepredetermined program in this case may be a program such as anapplication program or the like which is preset by the operator. Inparticular, this predetermined program can be a program to execute atleast one of the following: a processing operation to display apredetermined image on the display device or to stop the display, aprocessing operation to display information of predetermined selectionitems on the display device, a processing operation to turn the light ofan illuminator on or off or to cause the illuminator to flicker, aprocessing operation to generate or to stop the vibration of apredetermined rhythm and frequency pattern, a processing operation togenerate or to stop the sound of a predetermined tone, scale and rhythmpattern, and a processing operation to connect the mobile informationterminal to another information processing apparatus which can beconnected with the mobile information terminal through a network or todisconnect the connection. Based upon executing the processing operationto start or to stop this program, the operator can more easily recognizeone of the operation keys on which the finger of the operator performingan operation is placed, or the operator can easily execute apredetermined processing operation by half-depressing or touching anoperation key.

The mobile information terminal according to the present invention mayfurther comprise a gravity sensor for detecting whether gravity isapplied in a direction from a side of the display surface of the displaydevice to a side opposite to the side or whether gravity is applied inthe opposite direction, and the control section may execute a processingoperation to change the assignment of key codes to the operation keys,in response to an input signal from the gravity sensor.

Specifically, the assignment of the key codes to the operation keys canbe changed such that the arrangement of the key codes assigned to theoperation keys when the gravity is applied in the direction from theside of the display surface of the display device to the opposite side,that is, when the side of the display surface is directed upward, is amirror image of the arrangement of the key codes assigned to theoperation keys when the gravity is applied in the opposite direction,that is, when a surface of a side opposite to the side of the displaysurface is directed upward. Thereby, the arrangement of icons of theoperation keys displayed on the display device at the time when theoperator performs an input operation while directing the display surfaceto be pointed upward, that is, while viewing the display of the displaydevice, can be the same as the arrangement of the operation keys at thetime when the operator performs an input operation while directing aside opposite to the side of the display surface to be pointed upward,that is, while viewing the side on which the operation keys aredisposed. As a result, even when the operator performs an inputoperation while viewing the side on which the operation keys aredisposed, the operator can smoothly perform an input operation withoutbeing confused.

In a mobile information terminal that executes a processing operation todisplay operation keys disposed on a surface of a side opposite to theside of the display surface, the above-described processing operation tochange the assignment of the key codes, even if this processingoperation is executed independently from the processing operation tochange a display by using the finger position detecting mechanism, thatis, is executed in the mobile information terminal that does not executethis processing operation to change the display, works to improveoperability by matching the arrangement of icons of the operation keysdisplayed on the display device with the arrangement of the operationkeys at the time when the side that is opposite to the side of thedisplay surface is directed upward.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic view showing a condition in which a conventionalmobile information terminal is held in a hand.

FIG. 1B is a schematic view showing a condition in which a conventionalmobile information terminal is held in a hand.

FIG. 2A is a plan view of a conventional mobile information terminalthat shows both a front side and a rear side thereof.

FIG. 2B is a schematic view showing a condition in which the mobileinformation terminal shown in FIG. 2A is held in a hand.

FIG. 3A is a plan view of a mobile information terminal according to anembodiment of the present invention that shows both a front side and arear side thereof and positioned such that a front surface, on which adisplay surface of the mobile information terminal is arranged, isdirected upward.

FIG. 3B is a plan view on the rear side of the mobile informationterminal shown in FIG. 3A showing the condition in which the rear sideis directed upward.

FIG. 4 is a block diagram showing a general configuration of the mobileinformation terminal shown in FIGS. 3A and 3B.

FIG. 5 is a schematic view of a mobile information terminal according toan alternative embodiment to FIGS. 3A and 3B.

BEST MODE FOR CARRYING OUT THE INVENTION

As shown in FIGS. 3A and 3B, mobile information terminal 1 according tothis embodiment is provided with a display surface of display device 2disposed on front side 1 a thereof and a plurality of operation keys 3disposed on rear side 1 b opposite to front side 1 a. As shown in FIG.4, control section 5 composed of a computer and an electronic circuit isbuilt in this mobile information terminal 1. Operation signals ofoperation keys 3 are entered into control section 5, and display device2 displays various pieces of information under the control of controlsection 5.

In control section 5, programs are stored to make the computer ofcontrol section 5 execute various types of information processing,display control processing, and the like. Memory 6 used for varioustypes of processing operations executed in the computer is connected tocontrol section 5. Memory 6 can also store various types of informationinputted through operation keys 3. Further, mobile information terminal1 may be configured so that it can be connected to a radio communicationnetwork, as in a portable telephone. In this case, information, a newapplication program, or the like downloaded through the network may bestored in memory 6.

Mobile information terminal 1 is further provided with half-depressingsensor 4. When each key of operation keys 3 is depressed to some degree,even if these keys are not fully depressed, half-depressing sensor 4detects this. Further, mobile information terminal 1 is provided withgravity sensor 7 for detecting whether gravity is applied in a directionfrom front side 1 a to rear side 1 b or in the opposite direction.Detection signals from these sensors are entered into control section 5.

Next, input operation for mobile information terminal 1 according tothis embodiment is described.

Initially, a case where an operator holds mobile information terminal 1in his/her hand and performs an input operation while viewing thedisplay of display device 2 is described. In this case, as shown in FIG.3A, images (icons) of operation keys 3 are arranged and displayed ondisplay device 2 as if operation keys 3 are seen through intermediates.That is, the arranged icons, which include marks showing key codes suchas A, B, C,—in the example shown in FIG. 3A, the key codes beingrecognized in control section 5, when the corresponding key in operationkeys 3 is pressed, is displayed on display device 2. In this case, asseen from FIG. 3A, the arrangement of key codes, which are included inthe icons of operation keys 3 displayed on display device 2 and are seenfrom front side 1 a, is a mirror image of the arrangement of the keycodes which are seen from rear side 1 b, the key codes being recognizedin control section 5 when each of operation keys 3 is pressed.

Then, when a key of operation keys 3 is depressed to some degree but isnot fully depressed, that is, when the key of operation keys 3 is set ina condition in which it is half-depressed, control section 5 recognizesthis through half-depressing sensor 4 and executes the displayprocessing operation for display device 2 to indicate that the key ofoperation keys 3 is in the half-depressed condition. This displayprocessing operation can be implemented by changing an iconcorresponding to a half-depressed key in operation keys 3, that is, forexample, by changing a color, a figure, a display brightness and/or aflickering pattern of an icon of the half-depressed key in operationkeys 3 or by displaying a picture of a finger superimposed on the iconof the half-depressed key in operation keys 3. Further, when the key ofoperation keys 3 has been fully depressed, the display for indicatingthis may be implemented. In this case, it is preferable that any changein the display of display device 2, which occurs when a key ishalf-depressed, be different from any change in the display which occurswhen the key is fully depressed.

When the display operation described above has been performed, anoperator can determine, as regards a key of operation keys 3, that afinger of the operator operating operation keys 3, that are disposed onrear side 1 b, has been placed on the key before confirming a key codeto be inputted which is done by fully depressing the key of operationkeys 3. Therefore, by performing the press operation for a key ofoperation keys 3, while determining that one of operation keys 3 hasbeen half-depressed, the operator can accurately press a desired key ofoperation keys 3 without erroneously pressing a different key ofoperation keys 3.

At this time, icons of operation keys 3 can be simultaneously displayedwith the display of other information by displaying the icons ofoperation keys 3 such that they overlap with another display, or bydisplaying the icons of operation keys 3 in a display area that isdifferent from the display area where the other information isdisplayed. Further, icons of operation keys 3 may be displayed only whenany one of operation keys 3 is half-depressed, or icons of operationkeys 3 may be displayed by being exchanged with the other informationdisplayed on display device 2 only while any one of operation keys 3 ishalf-depressed.

Next, a case where mobile information terminal 1, according to thisembodiment, is operated in a condition in which mobile informationterminal 1 is viewed from rear side 1 b thereof, is described.

In this case, a key code that is recognized by control section 5 duringthe operation of a key of operation keys 3 is changed from a key codewhen an operator operates operation keys 3 while viewing display device2 in this embodiment. That is, the arrangement of key codes assigned tooperation keys 3 is set such that the arrangement, shown in FIG. 3B, atthe time when an operator holds mobile information terminal 1 whiledirecting rear side 1 b to be pointed upward, is a mirror image of thearrangement, shown in FIG. 3A, at the time when an operator holds mobileinformation terminal 1 while directing front side 1 a to be pointedupward. Therefore, the arrangement of key codes assigned to operationkeys 3 at the time when an operator holds mobile information terminal 1,while directing rear side 1 b to be pointed upward, is the same as thearrangement of icons of operation keys 3 displayed on display device 2at the time when an operator holds mobile information terminal 1, whiledirecting front side 1 a to be pointed upward. Accordingly, the operatorcan operate operation keys 3 without being confused even in a conditionin which an operator directs rear side 1 b to be pointed upward.

Control section 5 can control this switching of the assignment of keycodes to operation keys 3 by determining, in accordance with a detectionsignal from gravity sensor 7, whether mobile information terminal 1 isset in a condition in which front side 1 a is directed upward or is setin a condition in which rear side 1 b is directed upward. However, it isdesirable that this switching of the assignment of key codes tooperation keys 3 is not executed in some cases such as a case where thedetection operation of gravity sensor 7 becomes unstable due to theacceleration and deceleration of a vehicle when mobile informationterminal 1 is operated in the vehicle. Therefore, it is preferable thatthe switching function for key codes can be freely turned on and off.

Further, it is preferable that letters corresponding to key codesassigned to operation keys 3 when rear side 1 b is directed upward bemarked on operation keys 3 by printing in order to improve the ease ofoperation for operation keys 3 when rear side 1 b is directed upward. Inthis case, during an operation when front side 1 a is directed upward,key codes recognized in control section 5 at the time that each ofoperation keys 3 are operated, do not coincide with key codes marked onoperation keys 3. However, no confusion is generated as a result of themarking of letters on operation keys 3, during the operation, becausethe operator views display device 2 and does not view the letters thatare marked on operation keys 3 at this time.

Moreover, in mobile information terminal 1′, according to an alternativeembodiment shown in FIG. 5, sub-display device 8 whose size does notrestrict the layout area of operation keys 3, may be disposed on rearside 1 b. In this way, a key operation can be more easily performed whenrear side 1 b is directed upward. That is, for example, a characterstring inputted through operation keys 3 can be displayed on sub-displaydevice 8. Further, other information, such as information that indicatesthe input that has been performed, which is a desirable indication tohave during a key input operation, can be displayed on this sub-displaydevice 8.

As described above, according to the embodiments, an operator, who holdsmobile information terminal 1, 1′ in his/her hand and operates operationkeys 3 on rear side 1 b, while viewing the display of display device 2on front side 1 a, can determine the key of operation keys 3, on whichthe finger of the operator performing an operation is placed, inaccordance with a display of display device 2, by half-depressing thekey of operation keys 3 before confirming the key code of a letter orthe like that is to be inputted by the action of fully depressing thekey of operation keys 3. Accordingly, the operator can easily perform adesired key operation without making errors. Further, in mobileinformation terminals 1, 1′ according to the embodiments, thearrangement of operation keys 3 at the time that rear side 1 b isdirected upward can be made the same as the arrangement of icons ofoperation keys 3 displayed at the time that front side 1 a is directedupward. Thereby, an operator can perform an input operation withoutbecoming confused even in a case where the operator performs theoperation while viewing rear side 1 b.

In the embodiments, an example that uses half-depressing sensor 4 fordetecting that each of operation keys 3 is depressed half way isdescribed. However, a touch sensor for detecting that a finger toucheseach of operation keys 3 may be used instead of half-depressing sensor4. In this case, an operator can ascertain the position of his/herfinger just by touching any one of operation keys 3 without depressingit half way. Therefore, ease of the operation is further improved.

Further, both half-depressing sensor 4 and a touch sensor may beprovided. Thereby, control section 5 can recognize that different piecesof information are respectively inputted through the operation of onekey of operation keys 3 that corresponds to three types of conditions:when a key is lightly touched, when a key is depressed half-way and whena key is fully depressed. That is, various pieces of information can beinputted by a simple operation.

Moreover, control section 5 may execute or stop a predetermined programwhen any one of operation keys 3 is depressed half-way, or when any oneof operation keys 3 is lightly touched so that a predetermined functionis performed. For example, in mobile information terminal 1 having aconfiguration in which an illuminator is disposed in display device 2,the illuminator may be lighted when any one of operation keys 3 ishalf-depressed or lightly touched. Thereby, the display can be easilyseen during an operation. Further, as in a portable telephone, mobileinformation terminal 1 may be provided with a sound generating mechanismand/or a vibration generating mechanism, and one of following: aprocessing operation to display a predetermined image for apredetermined time or until a next operation is performed, a processingoperation to turn an illuminator on or off or to cause the illuminatorto flicker in a predetermined pattern, a processing operation togenerate or to stop a sound having a predetermined tone, scale, andrhythm pattern, a processing operation to generate or to stop avibration having a predetermined rhythm and frequency pattern, and acombination of these operations, may be executed when one predeterminedkey of operation keys 3 is half-depressed or lightly touched, or whensome predetermined keys of operation keys 3 are sequentiallyhalf-depressed or lightly touched in a predetermined order. These typesof processing operations may be performed for a purpose that an operatorcan more easily recognize any one of operation keys 3 that ishalf-depressed or has been lightly touched by the operator or may beexecuted for another purpose, that is, may be executed so as to executea desired processing operation by a simple operation. Moreover, thegenerated sound or vibration may be coded like Morse Code so as toinclude a plurality of pieces of information.

Furthermore, a processing operation to start and/or to stop anapplication program preset by an operator, a processing operation toconnect mobile information terminal 1 with another preset apparatusthrough a network to which mobile information terminal 1 can beconnected and to start and/or to stop communication with the apparatus,and/or a processing operation to display and/or to delete an imageindicating selection information such as a list of stored applicationprograms, may be executed when one or more predetermined keys ofoperation keys 3 are half-depressed or lightly touched. In a case wherethe image indicating selection information is displayed, the selectionoperation associated with this action may be performed with operationkeys 3. However, this operation may be performed with another inputdevice, which enables information to be input, without the need fordisplay device 2, such as through a touch sensor, a pointing device, anoperation key(s) disposed on front side 1 a or a side surface, or asmall number of operation keys which is disposed at another position ofrear side 1 b away from operation keys 3, or which has a size, a shapeand the like that are different from those of operation keys 3.

Furthermore, each key of operation keys 3 or some keys of operation keys3 that are placed at a predetermined positions may have their externalshape changed, may be provided with an irregular part having differentpatterns, and/or the roughness or softness of the surfaces thereof maybe changed, so that, when an operator touches a key of operation keys 3with his/her finger, the operator can recognize this particular key ofoperation keys 3 up to a point. Thereby, the operator can more easilyrecognize the position of a finger on rear side 1 b which is impossibleto see.

1. A mobile information terminal comprising: a display device having a display surface disposed on a front surface; a plurality of operation keys; a gravity sensor operable to detect whether gravity is applied in a direction from said front surface to a rear surface located on a reverse side of said front surface on which the display surface of said display device is disposed, or in a direction from said rear surface to said front surface; and a control section to which signals from said operation keys and said gravity sensor are entered and which can control the operation of said display device; wherein said control section is operable to execute a processing operation to change the assignment of key codes associated with said operation keys in response to an input signal from said gravity sensor.
 2. The mobile information terminal according to claim 1, wherein said control section is operable to execute a processing operation to cause said display device to display an image showing the arrangement of said operation keys.
 3. The mobile information terminal according to claim 1, wherein the arrangement of the key codes assigned to said operation keys when gravity is applied in a direction from said front surface to said rear surface is a mirror image of the arrangement of the key codes assigned to said operation keys when gravity is applied in a direction from said rear surface to said front surface.
 4. The mobile information terminal according to claim 2, wherein the arrangement of the key codes assigned to said operation keys when gravity is applied in a direction from said front surface to said rear surface is a mirror image of the arrangement of the key codes assigned to said operation keys when gravity is applied in a direction from said rear surface to said front surface.
 5. A mobile information terminal comprising: a plurality of operation keys having a key surface disposed on a front surface; a gravity sensor operable to detect whether gravity is applied in a direction from said front surface to a rear surface located on a reverse side of said front surface on which the key surface of said plurality of operation keys are disposed, or in a direction from said rear surface to said front surface; and a control section to which signals from said operation keys and said gravity sensor are entered, wherein said control section is operable to execute a processing operation to change the assignment of key codes associated with said operation keys in response to an input signal from said gravity sensor.
 6. The mobile information terminal according to claim 5, wherein the arrangement of the key codes assigned to said operation keys when gravity is applied in a direction from said front surface to said rear surface is a mirror image of the arrangement of the key codes assigned to said operation keys when gravity is applied in a direction from said rear surface to said front surface. 